With the rising costs and environmental concerns associated with fossil fuels, renewable energy sources have become increasingly important. The development of renewable fuel sources provides a means for reducing the dependence on fossil fuels. Accordingly, many different areas of renewable fuel research are currently being explored and developed.
With its low cost and wide availability, biomass has increasingly been emphasized as an ideal feedstock in renewable fuel research. Consequently, many different conversion processes have been developed that use biomass as a feedstock to produce useful bio-fuels and/or specialty chemicals. Existing biomass conversion processes include, for example, combustion, gasification, slow pyrolysis, fast pyrolysis, liquefaction, and enzymatic conversion. One of the useful products that may be derived from the aforementioned biomass conversion processes is a liquid product commonly referred to as “bio-oil.” Bio-oil may be processed into transportation fuels, hydrocarbon chemicals, and/or specialty chemicals.
Despite recent advancements in biomass conversion processes, many of the existing biomass conversion processes produce low-quality bio-oils containing high amounts of oxygen, which are difficult, if not impossible, to separate into various fractions. Due to the high amounts of oxygen present, in the bio-oil, these bio-oils require extensive secondary upgrading in order to be utilized as fuels or for further processing to obtain chemical products.
More specifically, the production of bio-oil by pyrolysis, both fast, and slow, can be problematic. Pyrolysis is characterized by the thermal decomposition of materials in an oxygen-poor or oxygen-free atmosphere (i.e., significantly less oxygen than required for complete combustion). In the past, pyrolysis has referred to slow pyrolysis whose equilibrium products included non-reactive solids (char and ash), liquids (tar and/or pyroligneous liquor), and non-condensable gases.
More recently, it has been recognized that pyrolysis can be carried out through a fast (rapid or flash) pyrolysis method where finely divided feedstock is rapidly heated and the reaction time is kept short, i.e. on the order of seconds. Such fast pyrolysis results in high yields of primary, non-equilibrium liquids and gases (including valuable chemicals, chemical intermediates, hydrocarbon chemicals and bio-fuels).
The non-equilibrium liquids (or bio-oil) produced by fast pyrolysis are suitable as a fuel for clean, controlled combustion in boilers and for use in diesel and stationary turbines. In fact, such bio-oil liquids offer some distinctive advantages for heating and power production over biomass gasification products and direct combustion of the biomass. Some of the advantages of bio-oil are:                Higher energy densities compared to direct combustion of, the raw biomass;        More easily/cost effective to transport and handle than raw biomass or producer gas;        Existing boilers may be used with bio-oil, subject only to retrofitting;        Fewer emissions in boiler use compared to solid fuels due to better control of the combustion process; and        Bio-oil from pyrolysis processes is the least cost liquid bio-fuel for stationary use and its net CO2-balance is better than that of other bio-fuels.        
However, besides all those advantages, instability and corrosiveness compared to conventional oil, have precluded a full success of pyrolysis bio-oils. Accordingly, it would be advantageous to develop a pyrolysis derived bio-oil that has improved stability and less corrosiveness than prior art bio-oils without having to undergo hydrotreating or other deoxygenating processes.